Organic electroluminescent device provided with a polarizing plate, a prism member and a phase member in a stacked arrangement

ABSTRACT

An organic EL light-emitting apparatus includes a base, an organic EL device, a prism member, a polarizing member, and a phase member. The prism member, the polarizing member, and the phase member are adjacent to a light extraction side of the organic EL device. The prism member includes a plurality of unit prisms each having a triangular-column shape. The unit prisms are arranged such that their longitudinal directions are parallel to one another. The polarizing member is disposed further from the base than the prism member. The prism member has an apex angle between 90° to 140°.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescent (EL)light-emitting apparatus including a prism member, a polarizing member,and a phase member disposed at a light extraction side.

2. Description of the Related Art

In a self-light-emitting device (e.g., an organic EL device), lightincident at an angle larger than a critical angle on an interface havinga larger index difference, such as that between a substrate of thedevice and air, is totally reflected. Therefore, actually onlyapproximately 20% of the total amount of emitted light can be extractedto the outside. To address this problem, a technique to increase theefficiency of light extraction by providing projections and depressionsto a light-extraction surface of the device is proposed.

One technique to increase brightness in a known display apparatus isdescribed in Japanese Patent Laid-Open No. 4-67016 and No. 6-308485. Thetechnique causes light from a backlight source to efficiently convergeto the front observation direction via a prism member having an optimalshape (e.g., triangular column, quadrangular pyramid) inserted in a pathover which the light is guided to a liquid crystal display panel.

Japanese Patent Laid-Open No. 2005-55481 discloses an organic EL panel,which has a self-light-emitting light source. With the aim ofsufficiently improving brightness, the organic EL panel is provided witha prism member.

Japanese Patent Laid-Open No. 2002-216947 discloses another organic ELpanel, which has a self-light-emitting light source. With the aim ofproviding the organic EL display apparatus with bright displayconditions with low power consumption, the organic EL panel is overlaidwith a circular polarizer and a microlens sheet.

Japanese Patent No. 3,543,951 discloses another organic EL panel, whichhas a self-light-emitting light source. With the aim of providing animage display apparatus that can increase brightness observed from thefront of a display screen without distorting a displayed image, theorganic EL panel is overlaid with a prism sheet and a circularpolarizing filter.

However, the above patent documents do not sufficiently study anapplication of a prism member to a light emitting apparatus thatprojects less glare of outside light. For an arrangement that has aprism member and a circular polarizer, the prism member contributes toan improvement in the efficiency of light extraction and the circularpolarizer contributes to a reduction in reflection of outside light.However, the prism member affects the reflection of outside light andthat property must be taken into account when reduction of glare isdesired. Japanese Patent No. 3,543,951, which is mentioned above,discloses an arrangement that has a prism sheet and a circularpolarizing filter, but does not describe the influence of the prismsheet on the reflection of outside light. It is necessary to considerthe positions and the structures of components in an arrangement thathas the prism member and the circular polarizer.

SUMMARY OF THE INVENTION

The present invention provides an organic EL light-emitting apparatusthat has efficiency of light extraction increased by the provision of aspecific prism member and a circular polarizer to a self-light-emittingdevice, such as an organic EL device. The EL light emitting apparatusemits more light by a reduction in the reflection of outside light.

An aspect of the present invention provides an organicelectroluminescent (EL) light-emitting apparatus which includes a base,an organic EL light-emitting device, a phase member, a polarizingmember, and a prism member. The organic EL light-emitting device isdisposed on the base and has a pair of electrodes and an organiccompound layer disposed between the pair of electrodes. The phase memberis adjacent to a light extraction side of the organic EL light-emittingdevice. The polarizing member is adjacent to a light extraction side ofthe phase member. The prism member is adjacent to a side of thepolarizing member that faces the base and includes a plurality of unitprisms each having a triangular-column shape. The unit prisms arearranged such that their longitudinal directions are parallel to oneanother. The prism member has an apex angle between 90° to 140°.

The present invention can improve efficiency of extracted light by theprovision of the prism member and the circular polarizer to theself-light-emitting device (e.g., organic EL device) and can reducereflection of outside light.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate exemplary arrangements that include opticalcomponents at a light extraction side of an organic EL device in adisplay panel according to an embodiment of the present invention.

FIG. 2 illustrates an exemplary structure of the organic EL device usedin an organic EL light-emitting apparatus according to an exemplaryembodiment of the present invention.

FIG. 3 illustrates a prism member used in the organic EL light-emittingapparatus.

FIG. 4 illustrates a characteristic of an emission angle of reflectionof incident outside light on a prism member having an apex angle of 45°and an incident angle of 15°.

FIG. 5 illustrates a characteristic of an emission angle of reflectionof incident outside light on a prism member having an apex angle of 140°and an incident angle of 15°.

FIG. 6 illustrates a characteristic of an emission angle to emissionintensity of an organic EL device laminated with a prism member havingan apex angle of 110°.

DESCRIPTION OF THE EMBODIMENTS

An organic EL light-emitting apparatus according to an exemplaryembodiment of the present invention includes an organic ELlight-emitting device that emits light in an organic compound layerdisposed between a pair of electrodes above a base. The organic ELlight-emitting apparatus also includes a prism member, a polarizingmember, and a phase member at a light extraction side of the organic ELlight-emitting device. The polarizing member converts natural light tolinearly polarized light and is called a linearly polarizing member. Thephase member generates an optical path difference for a quarter ofwavelength between linearly polarized light components oscillating indirections perpendicular to each other and is also called a λ/4 phasemember. The polarizing member and the phase member are also collectivelycalled a circular polarizer. The placement of these two members at thelight extraction side of the organic EL light-emitting device can reducereflection of outside light.

The prism member includes a plurality of unit prisms each having theshape of a triangular column. The unit prisms are arranged such thattheir longitudinal directions are parallel to one another. Morespecifically, for the prism member shown in FIG. 3, each of the unitprisms is indicated by a single projection or mountain of the prismmember. Each of the longitudinal direction axes shows an axial directionof the triangular column of the unit prism.

In the exemplary embodiment, the polarizing member is disposed closer tothe light extraction side than the prism member (i.e., disposed furtherfrom the base than the prism member). The prism member has an apex anglebetween 90° and 140°. The apex angle is indicated by θ shown in FIG. 3.The position of the polarizing member closer to the light extractionside than the prism member and the limitation of the apex angle to theabove numerical range enables the polarizing member to prevent lightreflected by the surface of the prism member from being emitted, thusreducing the reflection of outside light.

Exemplary embodiments of the present invention are described below withreference to the drawings.

FIG. 1A illustrates an organic EL light-emitting apparatus according toan exemplary embodiment of the present invention. The organic ELlight-emitting apparatus includes an organic EL device 10, a circularpolarizer 11 including a polarizing member and a phase member, and aprism member 12. In this exemplary embodiment, the polarizing member,the phase member, the prism member, and the organic EL device aredisposed in this order from a light extraction side A (i.e., from thetop side of the drawing).

Light emitted from the organic EL device 10 is refracted by a prismaticsurface while passing through the prism member 12. The refracted lightis converged to a front direction, passes through the circular polarizer11, and is extracted (dotted arrows) to an observation direction at thelight extraction side A.

In contrast, outside light incident from the outside of a panel passesthrough (solid arrows, B) the circular polarizer 11. A circularlypolarized light component passes through the prism member 12 and then isreflected by a reflecting electrode of the organic EL device 10. Therotation direction of the circularly polarized light is inverted whilebeing reflected. The reflected light passes through the prism member 12and then enters the circular polarizer 11. At this time, the circularlypolarized light component, which has the inverted rotation direction, isabsorbed. Therefore, incident outside light from the outside of thelight-emitting apparatus is not extracted to the observation direction,so the reflection of outside light is reduced.

FIG. 1B illustrates the organic EL light-emitting apparatus according toanother exemplary embodiment of the present invention. This organic ELlight-emitting device includes a polarizing member 13 and a phase member14. In this exemplary embodiment, the polarizing member, the prismmember, the phase member, and the organic EL device are positioned inthis order from the light extraction side A (i.e., from the top side ofthe drawing).

In this case, light emitted from the organic EL device is refractedwhile passing through the phase member 14 and the prism member 12. Therefracted light is converged to the front direction, passes through thepolarizing member 13, and then is extracted to the observationdirection. In contrast, outside light B incident from the outside of thepanel passes through the polarizing member 13. When a polarized lightcomponent passes through the prism member 12 and the phase member 14,the light component becomes circularly polarized light. The circularlypolarized light is reflected by the reflecting electrode of the organicEL device 10. The rotation direction of the circularly polarized lightis inverted while being reflected. When the reflected light passesthrough the phase member 14 and the prism member 12, the light becomeslinearly polarized light that is rotated 90°. The reflected light entersthe polarizing member 13. At this time, the polarized light component,which has been rotated 90°, is absorbed. Therefore, incident outsidelight from the outside of the light-emitting apparatus is not extractedto the observation direction, so the reflection of outside light isreduced.

As described above, incident light B that passes through the prismmember 12 tends to be absorbed and reflection of outside light isreduced. However, the inventors found that all the light reflected bythe surface of the prism member was not necessarily absorbed by thepolarizing member. That is, as will be described below, depending on theincident direction of the outside light and the apex angle of the prism,light reflected by the surface of the prism member may undesirably passthrough the polarizing member and be emitted to the exterior of theapparatus in some cases. Components included in the organic ELlight-emitting apparatus according to the exemplary embodiments aredescribed in greater detail below.

Prism Member

The prism member includes a plurality of projections opposite to asurface in contact with a light extraction surface of the organic ELdevice and transmits light. The projections according to the exemplaryembodiments are shaped such the longitudinal directions of the pluralityof unit prisms each having a triangular column are parallel to oneanother.

A prism member that has the shape of a triangular column is commerciallyavailable as a brightness enhancement film for background light, so anadvantage of introducing the prism member with low costs is offered.

The height and the shape of the bottom of each of the projections can beoptimized and the triangular columns can be laid such that the slope ofthe surface of the projection is close to a predetermined angle. Thebase can be about 1 μm to 100 μm and the height can be about 0.1 μm to200 μm.

For preventing the prism member from exhibiting color due to influenceof diffraction, the pitch width of the projections can be 1 μm or more.For avoiding image blurring when observing the panel, the pitch widthcan be a size (typically about 100 μm) that does not exceed the pixelpitch.

To produce the prism member, a pattern of projections is formed by theuse of a light-transmitting sheet. Examples of a material of the sheetinclude polymethyl methacrylate (PMMA), polycarbonate (PC), triacetylcellulose (TAC), and glass. These materials have substantially the sameindices of refraction (from 1.49 to 1.57).

For providing a circular polarizer at a light extraction side of theprism member to prevent reflection of outside light, a material that hassmaller birefringence can be selected as the material of the sheet.

To produce the projections, a resist pattern of projections is firstformed by photolithography, and a pattern-transferred mold ofdepressions is formed by electroforming. Then a pattern of projectionsis obtained by molding the light-transmitting sheet by heating andpressing using the mold of depressions. Alternatively, the pattern ofprojections is formed by a process of transferring a pattern ofprojections to the sheet using a photocurable resin and then curing thephotocurable resin with ultraviolet rays.

To produce a pattern of triangular-column projections used as abrightness enhancement film for backlight for a liquid crystal display,a cylindrical mold may be used. In this case, a cylinder subjected to aplanarization process by, for example, copper plating is rotated and cutby a diamond cutting tool so that a pattern of depressions having apredetermined grooved shape is formed. Then, a pattern of projections isformed by using the cylinder as in a printing process. That is, aphotocurable resin is placed in the grooves of the cylinder, and thepattern of projections is transferred to the surface of thelight-transmitting sheet by the photocurable resin while the cylinder isrotated. Then, the pattern of projections is cured by ultravioletradiation. This process is advantageous in that an excellent pattern ofprojections can be obtained even when the thickness of thelight-transmitting sheet member is reduced to several microns and themold and the prism member can be produced at low cost.

Polarizing Member (Linearly Polarizing Member)

The polarizing member is a filter that extracts linearly polarized lightthat oscillates only in a fixed or predetermined direction based onlight oscillating in all directions. For example, a uniaxially stretchedpolyvinyl alcohol film with absorbed oriented dichroic dye, such asiodine, can be used as the polarizing member. In this case, a stretcheddirection in a plane of the polarizing member is a direction of anabsorption axis, whereas a direction perpendicular thereto is adirection of a polarization axis. An absorption coefficient in thedirection of the absorption axis is larger than that in the direction ofthe polarization axis. Therefore, transmittance in the direction of theabsorption axis is smaller than that in the direction of thepolarization axis.

Phase Member (λ/4 Phase Member)

The phase member produces light with a phase difference from the lightin the polarized state emitted from the polarizing member. In theexemplary embodiments of the present invention, the phase memberprovides a phase difference of about λ/4 and functions to convert thepolarized state of linearly polarized light into that of circularlypolarized light and vice versa. One example of a material of the phasemember is a polycarbonate uniaxially stretched film.

Circular Polarizer

The circular polarizer is a laminated product of the polarizing memberand the phase member. In the exemplary embodiments, the polarizingmember is disposed at the light extraction side A (i.e., further fromthe base). Light passing through the circular polarizer is convertedinto circularly polarized light. Circularly polarized light passingthrough the circular polarizer is converted into linearly polarizedlight when passing through the phase member. Since circularly polarizedlight that passed through the circular polarizer once and was thenreflected, is converted into polarized light having a directionperpendicular to the polarizing member when passing through the circularpolarizer a second time, the light is absorbed by the polarizing memberand thus cannot pass therethrough.

Organic EL Device

The organic EL device can have a well-known structure and can be formedfrom well-known materials.

FIG. 2 is a cross-sectional view of an exemplary structure of atop-emission organic EL device. A substrate 21 provided with a drivingcircuit is overlaid with an organic EL film, including a hole transportlayer, a light-emitting layer, and an electron transport layer, byvacuum deposition.

The substrate 21 has chromium anode electrodes 22 each having athickness of 50 nm and an area of 100 μm² arranged at a pitch of 200 μmin the form of a two-dimensional pattern. A material of each of theanode electrodes may be aluminum or silver, which has a highreflectance, instead of chromium. To improve hole injection, aconductive transparent film, such as ITO and IZO, may be stacked on thesubstrate 21.

First, as a hole transport layer 23, which is an organic EL material, anα-NPD (α-naphtylphenyldiamine) layer having a thickness of 20 nm isstacked. Then, as a light-emitting layer 24, an Alq3(tris(8-hydroxyquinolinato)aluminum(III)) layer having a thickness of 30nm is stacked. Then, as an electron injection layer 25, a compositelayer of cesium carbonate and Alq3 having a thickness of 50 nm isstacked.

Then, as a transparent cathode electrode 26, an ITO layer having athickness of 60 nm is stacked by sputtering. In this manner, the organicEL device is formed. Similar EL devices can be conventionally formedusing well known compounds.

For this device structure, it is known that EL light emission of Alq3molecules occurs in an interface between the hole transport layer 23 andthe Alq3 light-emitting layer 24.

To prevent water from penetrating the organic EL film, as alight-transmitting protective film 27, a SiN layer having a thickness of640 nm is stacked by sputtering. In this manner, the formation oforganic EL device is completed.

Japanese Patent Laid-Open No. 11-97169 discloses that a layer formedfrom an oxide, a nitride, or a sulfide whose chief ingredient issilicon, boron, germanium, or other materials is suited for thelight-transmitting protective film. The film thickness for ensuringblocking effectiveness for oxygen and water is about 300 nm to 10 μm. Inconsideration of reducing the film stress and increasing productivity byreducing time of deposition, the thickness can be about 300 nm to 5 μm.The apex angle of the prism specified in the exemplary embodiments ofthe present invention will be described below.

Improvement in Light Extraction

To calculate efficiency of light extraction of EL light emission fordifferent apex angles of the prism, a commercially available ray tracingsimulation software application was used. The set conditions of the raytracing simulation are described below.

(1) Settings of Light Emission

EL light emission: Full diffusive light emission from the central planeof the light-emitting layer

Number of rays of light: 2000 Monte Carlo simulation

Number of Fresnel branches: 50

(2) Settings of Parameters in Structure System

Anode Electrode: Perfect Reflection

Light-emitting Layer: Index 1.70 Thickness 0.13 μm

Cathode Electrode: ITO Index 2.00 Thickness 0.05 μm

Protective Layer: Index 1.53 Thickness 50.0 μm

Prism: Index 1.53 Apex angle 20° to 160° Pitch width 20 μm End-faceFresnel reflection

The efficiency of light extraction was calculated by determining theratio of rays of light that passes through a top surface of the ELdevice (protective layer or prism) and heads toward the outside of thedevice with respect to all rays of emitted light. A flat type, in whichthe prism member was not included, was used as a comparative example.

Table 1 shows the simulation result of efficiency of light extractionfor an apex angle of the prism varying from 20° to 160°.

The efficiency of light extraction according to the exemplary embodimentincreased about slightly less than twice that of the flat type. However,when the apex angle exceeded 140°, the efficiency of light extractionaccording to the exemplary embodiment was close to that of the flattype. Therefore, from the viewpoint of improving the efficiency of lightextraction, the apex angle of the prism can be between 60° to 140°.

Antireflection for Outside Light

The consideration of antireflection for outside light is describedbelow. As described above, if the prism member merely transmits light,reflection of outside light can be prevented by a combination of theprism member and the circular polarizer.

However, the following factors are required to be considered.

(1) Since the prismatic surface has projections and depressions, thebehavior of outside light incident on the prismatic surface variesdepending on the incident angle with respect to the prismatic surface.

(2) A phase inversion occurs when the incident angle is large (55° ormore, as will be described below).

(3) The presence of phase inversion varies depending on the number ofreflections within the prism member.

In other words, the antireflection effects for outside light vary withthe incident angle of the outside light and the presence of the phaseinversion.

Table 2 shows the result of reflectance of natural light and p-polarizedlight with respect to the incident angle when natural outside lightenters a planar layer having an index of 1.5 from the air layer and alsoshows calculation of each phase change of both light on reflection, onthe assumption that the prism member in contact with the air layer wouldbe used. Here, the reflectance of the natural light is the average ofthat of the p-polarized light and that of s-polarized light.

When the incident angle is large, i.e., incidence occurs in a slantingdirection, both the p-polarized light and the natural light tend to havehigh reflectance. However, since an increase in the reflectance of thep-polarized light is smaller than that of the natural light, forreducing reflection by use of the prism member, the p-polarized lightcan be selected. For the p-polarized light, the reflectance is less than3% up to an incident angle of 65°.

The dependence of reflectance on the incident angle is described in, forexample, page 35, “Ohyo Kogaku”, TURUTA Tadao, Baifukan Co., Ltd. 1990.As will be described below, it is necessary to consider that the phaseinversion occurred for an incident angle larger than 55°.

For an arrangement illustrated in FIG. 1B, in the case of incidentoutside light from the outside of the panel at an incident angle smallerthan 55°, light that passed through the linearly polarizing member andthen was reflected by the surface of the prism member passes through thelinearly polarizing member and then exits out of the display panel. Thislight overlaps EL emitted light and thus causes glare, and as a result,display quality is degraded.

In the case of incident outside light at an incident angle larger than55°, since the phase inversion occurs when the light is reflected by thesurface of the prism member, the light is absorbed by the linearlypolarizing member and thus reflection of incident outside light does notoccur. In this case, reflection at an interface between the prism memberand the air is below 3% for all incident angles. With antireflection(AR) coating, it is easy to be below 1%.

As is obvious from the above, the antireflection effects for outsidelight vary with the incident angle of the outside light and the behaviorof the phase inversion.

Additionally, it is necessary to consider a phase inversion in the casein which light is reflected by the prismatic surface a plurality oftimes.

Outside light passes through the linearly polarizing member, and apolarized light component of the outside light enters the prismaticsurface of the prism member. Since the prismatic surface is inclined,the incident angle of the outside light is large because ofsuperposition. For example, outside light incident from a frontdirection on the surface of a prism that has an apex angle of 60° iseffectively 60° oblique incidence. In this case, the light is reflectedby the prismatic surface a plurality of times and this is observed asthe reflection of outside light. In particular, for a prism that has anapex angle smaller than 60°, a plurality of reflections occur in manyrays, so that the reflection of incident outside light is increased.

For the p-polarized light, when the incident angle is equal to orsmaller than 55°, the phase inversion does not occur; when the incidentangle is larger than 55°, the phase inversion occurs. For example, whenthe p-polarized light is reflected an even number of times at anincident angle of 55°, reflected light is not absorbed in the polarizer,so that the reflection of outside light occurs.

The above consideration reveals that, if outside light is reflected bythe prismatic surface more than once, an arrangement shown in FIG. 1Bcannot obtain sufficient antireflection for outside light. Anarrangement shown in FIG. 1A has a similar result.

In the case in which a plurality of reflections occur, as describedabove, a complex phase change occurs. Therefore, a simulation predictionby ray tracing is effective, and it is necessary to actually check thestate of reflection of outside light.

By ray tracing by use of the commercially available softwareapplication, which is described above, for different incident angles ofoutside light and different apex angles of the prism, the angle ofreflected light and the presence/absence of a plurality of reflectionswere examined. Unfortunately, when a plurality of reflections occurredand the incident angle on reflection was larger than 55°, the evaluationis ×. In contrast, when a plurality of reflections did not occur and theincident angle on reflection was smaller than 55°, the evaluation is ◯.When two reflections occurred in only a specific incident angle ofoutside light (the front) (the incident angle on reflection was smallerthan 55°), the evaluation is Δ.

Table 3 shows the result of this experiment. For an apex angle of theprism of 60° or less, a plurality of reflections occurred in almost allof the incident angles, and therefore, antireflection effects foroutside light is not expected. For an apex angle of the prism between90° and 120°, two reflections slightly occurred in the case of outsidelight incident from the front direction. For an apex angle of the prismof 130° or more, only one reflection occurred and the incident angle onreflection was smaller than 55°, and therefore, excellent antireflectioneffects for outside light are expected.

FIGS. 4 and 5 show simulation examples. FIG. 4 shows an example of anevaluation of ×. On a condition that the apex angle of the prism is 45°and outside light is incident at an angle of 15°, multiple reflectionswill occur in almost all rays. FIG. 5 shows an example of an evaluationof ◯. On a condition that the apex angle of the prism is 140° andoutside light is incident at an angle of 15°, only one reflection occursand the incident angle on the prismatic surface is 5° and 55°.

The above consideration and simulation reveals that an apex angle of theprism of 90° or more can reduce the reflection of outside light.

The foregoing shows that, for improving the efficiency of lightextraction, while at the same time reducing the reflection of outsidelight, the apex angle of the prism can be between 90° and 140°.

EXAMPLES

The present invention will be described in greater detail with referenceto examples.

Example 1 About Efficiency of Light Extraction

An organic EL light-emitting apparatus that included a prism member wasproduced by the following steps.

First, a device illustrated in FIG. 1A was produced. A pattern oftriangular column prisms each having an apex angle of 110° at a pitch of15 μm was formed on an optically isotropic film (sheet of a thickness of70 μm) by being transferred by ultraviolet curing of an acrylicphotocurable resin. This corresponds to the prism member. Additionally,a circular polarizer (a sheet of RD-HL56-W03 from Sanritz Corporation,having a thickness of 100 μm) was provided.

The production of the apparatus according to the exemplary embodiment iscompleted by laminating an organic EL device, the above prism member,and the circular polarizer together. This is referred to as a laminatedmember 1.

Then, a device illustrated in FIG. 1B was produced. A pattern oftriangular column prisms each having an apex angle of 110° at a pitch of15 μm was formed on a reversed wavelength dispersion λ/4 phase plate (asheet of a copolycarbonate film having a thickness of 70 μm) by beingtransferred by ultraviolet curing of an acrylic photocurable resin. Thiscorresponds to the prism member and the polarizing member. Additionally,a linear polarizer (a sheet of LLC2-82-18 from Sanritz Corporation,having a thickness of 100 μm) was provided. The production of theapparatus according to the exemplary embodiment is completed bylaminating the organic EL device, the above reversed wavelengthdispersion λ/4 phase plate, and a linearly polarizing member together.This is referred to as a laminated member 2.

In the case in which the organic EL light-emitting apparatus is appliedto a display apparatus, when the main observation direction is fixed,the device and the members can be laminated together such that thelongitudinal direction of the prism member is substantially aligned withthe lateral direction of the panel. This is because, for a horizontallyoriented panel, i.e., a rectangular panel, generally, a direction of alonger side seen from the front is observed as the lateral position. Thelamination described above achieves a reduction in degradation ofbrightness even the panel is observed obliquely in the lateraldirection.

The members can be laminated together such that the direction of theabsorption axis of the polarizing member is substantially perpendicularto the longitudinal direction of the prism member. In this case,interference fringes are not exhibited when outside light is reflected.

An arrangement in which only the organic EL device and the circularpolarizer are laminated together is referred to as a ref 1.

In this example, the prismatic surface has an apex angle of 110°.Therefore, the quantity of a horizontally extracted light component,including light that would not be extracted due to total reflection in aknown plane, is large.

FIG. 6 shows the dependence of emission intensity on the emission angleof the organic EL device with the prism member having an apex angle of110° measured with a brightness meter. For both the laminated members 1and 2, in which the organic EL device and the prism member having anapex angle of 110° were laminated together, the emission intensity inthe front increased about 1.4 times the ref 1. Here, the emission anglein the front direction is 0°.

Table 5 shows the result of an examination for determining thedependence of the emission intensity on an angle in the front directionwhen the prism has an apex angle that varies from 20° to 170°. The ratioof emission intensity in the front indicates a ratio to a flat devicethat does not include a prism (ref 1).

For an apex angle of 50° or more, the emission intensity in the frontdirection was large. However, for an apex angle of more than 120°, theemission intensity in a slanting direction decreased. For an apex angleof more than 150°, the emission intensity had similar characteristics tothat in the ref 1.

Therefore, from the viewpoint of improving the efficiency of lightextraction, the apex angle of the prism can be between 50° and 140°, atwhich a component of light that exits in the front direction has a largequantity than that of the ref 1.

Example 2 About Antireflection for Outside Light

To evaluate influence of reflection of outside light, a glass substratewith aluminum evaporated thereon was provided. Prism members havingdifferent apex angles were bonded to the respective substrates with anacrylic resin. Each of the bonded composites was overlaid with acircular polarizer. The influence of reflection of outside light onthese samples were observed and evaluated by use ofGonio-Spectrophotometric Color Measurement System GCMS-11 from MurakamiColor Research Laboratory Co., Ltd. More specifically, each sample wasirradiated with substantially parallel rays of light from a standardwhite-light source (xenon lamp) while the incident angle was varied, andthe surface of each sample was observed.

Table 4 shows the result of this experiment. When the surface lookedblack seen from the front and slanting directions (antireflection foroutside light was effective), the evaluation is ◯. Unfortunately, whenthe surface looked whitish due to reflection from the surface of theprism member, the evaluation is x. When reflection from the prism memberwas recognized if observed carefully, the evaluation is Δ.

Similarly, to evaluate influence of reflection of outside light, anotherglass substrate with aluminum evaporated thereon was provided. A sheetthat included a prism pattern for each of different apex angles formedon a reversed wavelength dispersion λ/4 phase plate was bonded to thesubstrate with an acrylic resin. Each of the bonded composites wasoverlaid with a linearly polarizing member. The influence of reflectionof outside light on these samples were observed and evaluated in asimilar way described above.

The result of this experiment is also shown in Table 4. This resultsubstantially matches with a result that a plurality of reflectionsincrease the reflection of outside light, which was obtained in thesimulation prediction shown in Table 3. For each of the panels achievingan evaluation of ◯, it was difficult to recognize the prism member. Foreach of the panels of an evaluation of ×, the prism member was lookedwhitish. In particular, for panels that included a prism member that hadan apex angle of 60° or less, the prism member was looked noticeablywhite.

When these samples were observed outdoors in clear weather, a samplethat included the circular polarizer had antireflection effects foroutside light in the case in which the prism member had an apex angle of100° or more. A sample that included the linear polarizer and the λ/4phase plate had antireflection effects for outside light in the case inwhich the prism member had an apex angle of 90° or more. This resultmatches with the results shown in Tables 3 and 4.

Therefore, from the viewpoint of antireflection for outside light, theapex angle of the prism can be 90° or more.

P-polarized light that has passed through the prism member (converted tocircularly polarized light by passing through the λ/4 phase plate) orcircularly polarized light that has passed through the prism member arereflected by the reflecting electrode in the organic EL device. Sincethe reflected light is inverted and thus absorbed by the linearlypolarizing member or the circular polarizer, incident outside light isnot reflected finally, and antireflection effects for outside light areobtained.

The results of the above examples reveal that an apex angle of the prismthat achieves both an improvement in the efficiency of light extractionand antireflection for outside light is between 90° and 140°.

TABLE 1 VARIATIONS IN EFFICIENCY OF LIGHT EXTRACTION FOR DIFFERENT APEXANGLES OF PRISM EFFICIENCY OF LIGHT APEX ANGLE (°) EXTRACTION (%)  20 29 30 35.7  40 37.4  60 40.5  90 39.2 120 39.8 140 40 160 35.8 FLAT TYPE20.8 (COMPARATIVE EXAMPLE)

TABLE 2 REFLECTANCE CHARACTERISTICS OF P-POLARIZED LIGHT AND CIRCULARLYPOLARIZED LIGHT AT INTERFACE BETWEEN AIR AND LAYER WITH INDEX OF 1.5REFLECTANCE PHASE CHANGE REFLECTANCE PHASE CHANGE INCIDENT OFP-POLARIZED IN P-POLARIZED OF NATURAL IN NATURAL ANGLE (°) LIGHT (%)LIGHT (°) LIGHT (%) LIGHT (°) 0 3.1 5.2 3.1 180 5 3.1 5.2 3.1 180 10 35.2 3.1 180.1 15 2.8 5.1 3.1 180.2 20 2.5 5 3.1 180.4 25 2.2 4.9 3.1180.6 30 1.8 4.8 3.1 180.9 35 1.4 4.7 3.2 181.3 40 0.9 4.7 3.4 181.9 450.5 5 3.8 182.8 50 0.1 6.9 4.4 185.2 55 0 151.3 5.5 330.1 60 0.3 178.57.3 357.8 65 1.6 179.7 10.3 359.5 70 4.7 180 15.2 0 75 11.2 180.1 23.30.2 80 24.2 180 37 0.2 85 49.8 180 60 0.1

TABLE 3 SIMULATION RESULTS OF REFLECTION OF OUTSIDE LIGHT FOR DIFFERENTAPEX ANGLES OF PRISM AND DIFFERENT INCIDENT ANGLES OF OUTSIDE LIGHTPRESENCE/ABSENCE INCIDENT OF TWO REFLECTIONS ANGLE AT INCIDENCE ON APEXANGLE (VERTICAL: 0) PRISMATIC SURFACE OF PRISM (°) 15 30 45 60 80 45 X XX ◯ X 60 X X X ◯ 90 ◯ - X ◯-Δ ◯ ◯ ◯ 120 ◯ ◯-Δ ◯ ◯ ◯ 140 ◯ ◯ ◯ ◯ ◯ 160 ◯◯ ◯ ◯ ◯ ◯: TWO REFLECTIONS DID NOT OCCUR Δ: TWO REFLECTIONS SLIGHTLYOCCURRED X: TWO REFLECTIONS OCCURRED

TABLE 4 EVALUATION RESULTS OF REFLECTION OF OUTSIDE LIGHT FOR DIFFERENTAPEX ANGLES OF PRISM AND DIFFERENT INCIDENT ANGLES OF OUTSIDE LIGHTINCIDENT APEX ANGLE ANGLE OF (VERTICAL: 0) PRISM (°) 15 30 45 60 80 WITHCIRCULAR POLARIZER (FIG. 1A)  45 X X X X X  60 X X X ◯ ◯  70 X X X Δ Δ 80 X X Δ Δ Δ  90 ◯ Δ Δ ◯ ◯ 100 ◯ ◯ ◯ ◯ ◯ 110 ◯ ◯ ◯ ◯ ◯ 120 ◯ ◯ ◯ ◯ ◯140 ◯ ◯ ◯ ◯ ◯ 160 ◯ ◯ ◯ ◯ ◯ WITH POLARIZING MEMBER AND PHASE MEMBER(FIG. 1B)  45 X X X X X  60 X X X ◯ ◯  70 Δ Δ ◯ Δ ◯  80 Δ ◯ ◯ ◯ ◯  90 ◯◯ ◯ ◯ ◯ 100 ◯ ◯ ◯ ◯ ◯ 110 ◯ ◯ ◯ ◯ ◯ 120 ◯ ◯ ◯ ◯ ◯ 140 ◯ ◯ ◯ ◯ ◯ 160 ◯ ◯◯ ◯ ◯ ◯: BLACK Δ: SLIGHTLY WHITISH X: CONSIDERABLE WHITE

TABLE 5 RATIO OF EMISSION INTENSITY OF DEVICE IN FRONT FOR DIFFERENTAPEX ANGLES OF PRISM RATIO OF EMISSION APEX ANGLE (°) INTENSITY IN FRONT20 0.8 30 0.9 40 1 50 1.1 60 1.1 70 1.3 80 1.4 90 1.5 100 1.4 110 1.4120 1.4 130 1.3 140 1.1 150 1 160 1 170 1.1

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions.

This application claims the benefit of Japanese Application No.2006-098001 filed Mar. 31, 2006, which is hereby incorporated byreference herein in its entirety.

1. An organic electroluminescent light-emitting apparatus comprising: abase; an organic electroluminescent light-emitting device on the base,the organic electroluminescent light-emitting device having a pair ofelectrodes and an organic compound layer disposed between the pair ofelectrodes; a phase member adjacent to a light extraction side of theorganic electroluminescent light-emitting device; a polarizing memberadjacent to a light extraction side of the phase member; and a prismmember adjacent to a side of the polarizing member that faces the base,the prism member including a plurality of unit prisms each having atriangular-column shape, the unit prisms being arranged such that theirlongitudinal directions are parallel to one another, wherein the prismmember has an apex angle between 90° to 140° and wherein the polarizingmember, the prism member, the phase member, and the organicelectroluminescent light-emitting device are arranged in this order fromthe light extraction side.
 2. An organic electroluminescentlight-emitting apparatus, comprising: a base; an organicelectroluminescent light-emitting device on the base, the organicelectroluminescent light-emitting device having a pair of electrodes andan organic compound layer disposed between the pair of electrodes; aphase member adjacent to a light extraction side of the organicelectroluminescent light-emitting device; a polarizing member adjacentto a light extraction side of the phase member; and a prism memberadjacent to a side of the polarizing member that faces the base, theprism member including a plurality of unit prisms each having atriangular-column shape, the unit prisms being arranged such that theirlongitudinal directions are parallel to one another, wherein the prismmember has an apex angle between 90° to 140°, and wherein an absorptionaxis of the polarizing member is substantially perpendicular to alongitudinal direction of the prism member.